Field of the Invention
The present invention relates to an expanding method and apparatus for expanding an expandable sheet having a central portion and a peripheral portion formed around the central portion, the central portion of the expandable sheet being attached to the back side of a workpiece, the peripheral portion of the expandable sheet being attached to an annular frame having a central opening, the workpiece being located in the central opening of the annular frame.
Description of the Related Art
As a method of dividing a workpiece such as a wafer into individual chips, there is a method including the steps of applying a laser beam to the workpiece along division lines in the condition where the laser beam is focused inside the workpiece to thereby form a modified layer inside the workpiece along each division line, and next applying an external force to the workpiece to thereby break the workpiece along each modified layer, thus dividing the workpiece into the individual chips as increasing the spacing between any adjacent ones of the individual chips. As an apparatus for dividing the workpiece by applying an external force as mentioned above, there has been proposed a work dividing apparatus described in Japanese Patent Laid-Open No. 2010-206136, for example. In this work dividing apparatus, a wafer is supported through an expandable sheet to an annular frame, and a modified layer is previously formed inside the wafer along each division line as a division start point. This wafer is divided along each modified layer by applying an external force from dividing means. Thereafter, the annular frame is held by frame holding means, and the wafer is held through the expandable sheet on a holding table under suction. In this condition, an annular area of the expandable sheet as defined between the outer circumference of the wafer and the inner circumference of the annular frame is heated by a heater to thereby heat-shrink the annular area. As a result, the spacing between the adjacent chips divided from the wafer is maintained.